An electrical impedance imaging tactile sensor for underwater structure inspection

Abstract

This invention discloses a resistive impedance imaging tactile sensor for underwater structure detection, comprising a flexible conductive sensing layer and an insulating encapsulation layer arranged sequentially from the inside out. The flexible conductive sensing layer includes an electrode layer and a flexible conductive layer, wherein the surface of the electrode layer has a microgroove structure. The flexible conductive layer and the electrode layer are stacked and embedded in the microgroove to form a mechanical interlocking structure. The insulating encapsulation layer includes a flexible insulating layer and a shielding layer, which are bonded together without adhesive to form a sealed encapsulation structure. This sensor achieves highly reliable interlayer bonding and sealing without adhesives, effectively avoiding performance failure caused by adhesive hydrolysis, interface delamination, or moisture penetration in the underwater environment. It is suitable for long-term, stable underwater resistive impedance imaging detection.

Description

Technical Field

[0001] This invention relates to the field of underwater inspection and flexible sensing technology, and in particular to an electrical impedance imaging tactile sensor for underwater structure inspection. Background Technology

[0002] With the rapid development of deep-sea engineering equipment, subsea pipelines, and underwater robotic systems, the demand for non-destructive testing of underwater structures is increasing. Traditional optical imaging is limited by issues such as scattering by suspended particles in water, light attenuation, light spot diffusion, and red light absorption, making it difficult to obtain continuous and stable surface details in turbid water environments. Although sonar imaging has a certain degree of penetration, its resolution is limited by factors such as frequency band, transducer aperture, and multipath interference, making it difficult to accurately describe surface damage features such as fine cracks, local depressions, and structural wear. Therefore, developing tactile sensing technologies independent of underwater photoacoustic conditions has become an important trend in the field of marine engineering. In recent years, Electrical Impedance Tomography (EIT), with its wireless flexible structure, large-area deployment capability, and ability to reconstruct surface morphology in real time, has become an important direction in underwater tactile sensing research. However, existing flexible EIT sensors generally employ a stacked structure of polydimethylsiloxane-metal electrode-conductive thin film, with interlayer fixation relying on adhesives. In seawater, this structure is prone to hydrolytic failure, interfacial delamination, and water penetration. Furthermore, the lack of an effective mechanical interlocking structure between the metal electrode and the flexible conductive layer leads to increased interfacial resistance under underwater vibration and shear stress, severely impacting imaging stability. Additionally, the sensor's outer layer lacks a corrosion-resistant sealing structure, making electrode oxidation and delamination from the sensing layer difficult to avoid during long-term service. Summary of the Invention

[0003] This invention provides an impedance imaging tactile sensor for underwater structure detection, thereby overcoming the aforementioned technical problems.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: An impedance imaging tactile sensor for underwater structure detection, characterized in that it comprises a flexible conductive sensing layer and an insulating encapsulation layer arranged sequentially from the inside to the outside; The flexible conductive sensing layer includes an electrode layer and a flexible conductive layer. The surface of the electrode layer is provided with a microgroove structure. The flexible conductive layer is stacked with the electrode layer and embedded in the microgroove structure to form a mechanical interlocking structure. The insulating encapsulation layer includes a flexible insulating layer and a shielding layer, which are bonded together without glue to form an encapsulation structure.

[0005] Furthermore, the electrode layer is an EIT electrode, and the EIT electrode has a plurality of electrode contacts evenly arranged axially; the flexible conductive layer leads out a plurality of electrode leads along the circumferential direction, and the electrode leads are connected to the electrode contacts.

[0006] Furthermore, the material of the shielding layer is cast polypropylene.

[0007] Furthermore, the EIT electrode is a copper foil substrate with a thickness of 20–80 μm.

[0008] Furthermore, the depth of the microgroove structure is 10–60 μm.

[0009] Furthermore, the microgroove structure is formed by femtosecond laser etching.

[0010] Furthermore, the flexible insulating layer is made of any one of TPU, PET, or polyolefin films.

[0011] Beneficial Effects: This invention utilizes a hot-melt encapsulation process between the flexible insulating layer and the shielding layer, creating a continuous molecular chain fusion structure at the encapsulation interface. This eliminates the need for adhesives and avoids the generation of hydrolysis byproducts. The interface is free of delamination, pores, and permeation channels, significantly improving the sensor's sealing stability in harsh environments such as deep water, high humidity, and long-term immersion. The electrode layer employs copper foil with a microgroove structure. During the stacking or compression of the flexible conductive layer, the conductive material embeds into the grooves, forming a robust mechanical interlock. Simultaneously, the groove geometry effectively increases the contact area between the electrode and the conductive layer, achieving stable and reliable electrical coupling. This allows the electrode to maintain high adhesion strength, low impedance, and stable electrical transmission performance even under complex conditions such as underwater vibration, impact, bending, and fatigue, completely avoiding the impedance drift problem caused by interface peeling or contact degradation in traditional planar electrodes. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the overall structure of the electrical impedance imaging tactile sensor for underwater structure detection disclosed in this invention. Figure 2 This is an exploded view of the overall structure of the electrical impedance imaging tactile sensor for underwater structure detection disclosed in this invention; Figure 3A schematic diagram of the latching interface of an impedance imaging tactile sensor for underwater structure detection disclosed in this invention; Figure 4 This is a schematic diagram of the overall workflow of the electrical impedance imaging tactile sensor for underwater structure detection disclosed in this invention. In the figure: 1-Insulating encapsulation layer; 101-Flexible insulating layer; 102-Shielding layer; 2-Electrode layer; 201-Micro trench structure; 3-Flexible conductive layer; 4-Electrode lead. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] This embodiment provides a resistive impedance imaging tactile sensor for underwater structure detection, such as... Figures 1 to 4 As shown, it includes a flexible conductive sensing layer and an insulating encapsulation layer 1 arranged sequentially from the inside to the outside; The flexible conductive sensing layer includes an electrode layer 2 and a flexible conductive layer 3. The surface of the electrode layer 2 is provided with a microgroove structure 201. The flexible conductive layer 3 is stacked with the electrode layer 2 and embedded in the microgroove structure 201 to form a mechanical interlocking structure. The insulating encapsulation layer 1 includes a flexible insulating layer 101 and a shielding layer 102. The flexible insulating layer 101 and the shielding layer 102 are bonded together in a glue-free manner to form an encapsulation structure.

[0016] The insulating encapsulation layer 1 forms the outermost layer of the sensor, preventing seawater from directly eroding the internal functional layers and providing external protection against scratches and impacts. The flexible insulating layer 101 and the shielding layer 102 are tightly bonded together by hot pressing. During the hot-melt process, the shielding layer 102 undergoes continuous melting and molecular chain cross-linking at the interface with the flexible insulating layer 101, thereby forming a dense, glue-free, and highly reliable encapsulation structure. This effectively avoids delamination, peeling, and water seepage problems caused by adhesive hydrolysis during long-term underwater use.

[0017] A microgroove structure 201 is provided on the electrode layer 2. The presence of the microgroove structure 201 increases the effective contact area between the flexible conductive layer 3 and the electrode layer 2, achieving low-impedance interface coupling, i.e., forming an electrical interlocking effect. This structure ensures stable underwater electrode adhesion without the need for glue or additional conductive materials, avoiding the interface impedance drift problem faced by traditional planar electrode structures under seawater vibration and impact conditions. During assembly, the flexible conductive layer 3 and the electrode layer 2 are stacked and pressed together, so that the flexible conductive layer 3 is partially embedded in the microgroove structure 201 on the surface of the electrode layer 2, forming a mechanical interlocking structure, thus constituting a complete flexible conductive sensing layer. Finally, the insulating encapsulation layer 1 is wrapped around the outside of the flexible conductive sensing layer to complete the overall encapsulation of the sensor.

[0018] Furthermore, the electrode layer is an EIT electrode, and the EIT electrode is provided with a number of electrode contacts evenly arranged axially; the flexible conductive layer 3 extends out multiple electrode leads 4 in the circumferential direction, and the electrode leads 4 are connected to the electrode contacts to realize the functions of current injection and voltage acquisition.

[0019] The EIT (Electronic Induction Technology) operating mode can employ adjacent excitation, skip excitation, or symmetrical excitation. By injecting a low-frequency, stable alternating current into one electrode pair and sampling voltage changes on the remaining electrodes, boundary electrical signals can be obtained. After processing the sampled data using the EIT image reconstruction algorithm, a two-dimensional pressure or topographic distribution map of the target surface can be obtained, enabling crack identification, defect localization, or contour modeling. Flexible sensors can be attached to the surface of underwater pipelines, ship hull structures, or equipment shells, utilizing their flexible structure to achieve large-area coverage. Due to the sensor's flexibility, low profile, and advantages such as strong structural encapsulation, high water resistance, and strong corrosion resistance, it can be permanently fixed to underwater inspection robot arms, detector ends, or fixed monitoring equipment, maintaining reliable operation even in complex environments such as deep water pressure, fluid impact, structural bending, and periodic vibration.

[0020] Furthermore, the material of the shielding layer 102 is cast polypropylene. Cast polypropylene has excellent density, low water absorption and good dielectric properties. When used as a shielding layer, it can not only effectively block external water vapor and ion penetration, but also provide a stable electromagnetic environment without introducing additional conductive paths, thus avoiding interference of stray currents in the seawater environment on the impedance imaging signal.

[0021] Furthermore, the EIT electrode is a copper foil substrate with a thickness of 20–80 μm. This thickness can be adjusted according to the sensor's flexibility requirements and the sensitivity of the EIT signal acquisition.

[0022] Furthermore, the depth of the microgroove structure 201 is 10–60 μm, and the groove width and spacing can be precisely set according to the required EIT acquisition resolution.

[0023] Furthermore, the microtrench structure 201 is formed by femtosecond laser etching. Femtosecond laser etching has a very small heat-affected zone, which can avoid problems such as local melting, burrs, and warping caused by traditional mechanical etching and CO2 laser etching, keeping the trench sidewalls vertical and flat, which is conducive to the embedding of the flexible conductive layer with it.

[0024] Furthermore, the flexible insulating layer 101 is made of any one of TPU, PET, or polyolefin films, and its thickness can be selected according to the pressure environment of the underwater application. These materials all have excellent flexibility, hydrolysis resistance, and chemical stability, and can maintain structural integrity in the underwater environment for a long time. At the same time, their good heat-melting properties facilitate glue-free encapsulation with the shielding layer 102, effectively preventing moisture penetration and interface delamination, and improving the overall sealing performance and service reliability of the sensor.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A resistive impedance imaging tactile sensor for underwater structure inspection, characterized in that: It includes a flexible conductive sensing layer and an insulating encapsulation layer arranged sequentially from the inside to the outside (1); The flexible conductive sensing layer includes an electrode layer (2) and a flexible conductive layer (3). The surface of the electrode layer (2) is provided with a microgroove structure (201). The flexible conductive layer (3) is stacked with the electrode layer (2) and embedded in the microgroove structure (201) to form a mechanical interlocking structure. The insulating encapsulation layer (1) includes a flexible insulating layer (101) and a shielding layer (102). The flexible insulating layer (101) and the shielding layer (102) are bonded together in a glue-free manner to form an encapsulation structure.

2. The impedance imaging tactile sensor for underwater structure detection according to claim 1, characterized in that: The electrode layer is an EIT electrode, and the EIT electrode is uniformly arranged with several electrode contacts along the axial direction; the flexible conductive layer (3) leads out multiple electrode leads (4) along the circumferential direction, and the electrode leads are connected to the electrode contacts.

3. The impedance imaging tactile sensor for underwater structure detection according to claim 1, characterized in that: The material of the shielding layer (102) is cast polypropylene.

4. The impedance imaging tactile sensor for underwater structure detection according to claim 2, characterized in that: The EIT electrode is a copper foil substrate with a thickness of 20–80 μm.

5. The impedance imaging tactile sensor for underwater structure detection according to claim 1, characterized in that, The depth of the microgroove structure (201) is 10–60 μm.

6. The impedance imaging tactile sensor for underwater structure detection according to claim 1, characterized in that, The microgroove structure (201) is formed by femtosecond laser etching.

7. The impedance imaging tactile sensor for underwater structure detection according to claim 1, characterized in that: The flexible insulating layer (101) is made of any one of TPU, PET, or polyolefin films.

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